Installing Roll Roofing

For a utilitarian solution when appearance isn't as important, consider roll roofing, which is made of materials similar to composition shingles but generally not as durable. Be sure to check the warranty, which may be for only one year. If you install roll roofing using the double-coverage method, it will last longer.

Roll roofing is often installed over bare wood sheathing or sheathing that has been painted with a primer. Applying roofing felt first will better protect the sheathing against condensation, as well as against leaking.

If the roof is sloped, you can use the exposed-nail method. For a slightly sloped roof, use the concealed-nail method shown in the box, below right. For a flat or nearly flat roof, use double coverage, although a torch-down modified bitumen or EPDM roof is a better solution.

Prestart Checklist

Time
Working with a helper, half a day to install flashings and roll roofing for a 700-square-foot roof with modest complications

Install drip-edge flashings, roofing felt, and perhaps WSU. You can install metal valley flashing, but it is common to simply apply an 18-inch-wide strip of roll roofing instead. Set it in a bed of roofing cement, smooth out any creases, and drive nails near the edges.

Cut strips of roofing 9 inches wide, position them flush with the drip edges along the eave and rake, and attach them by driving two rows of nails that are about 3 inches apart. Use a trowel to spread roofing cement over half or more of the strips.

Step 2

Position the first course so it overhangs the drip edges by about 1/4 inch and roll it out a distance of 8 feet or so. Drive nails every 3 inches along the rake at one end, pull it taut, and drive nails along the eave edge. The nails should be about 1 inch from the edges. For extra protection add a 3-foot-wide strip on top of the 18-incher.

Set the first course in the cement so it overhangs by about 1/4 inch. Position and roll out the roofing carefully because it is not easy to reposition, then press it into the cement. Nail only its top edge (the part that is bare of mineral coating). Coat the top edge with a 4- to 6-inch-wide layer of roofing cement and apply the next courses in the same way.

Step 3

The next sheet overlaps the first by 4 inches or with some types of roll roofing, enough to cover the area that is bare of mineral surfacing. Snap a chalkline indicating the top of the next sheet, roll it out along the line, and drive nails as for the first sheet.

To seal a plumbing vent, spread roofingcement around the pipe. Cut a hole in a piece of roofing about 2 feet wide and slip it over the pipe. The piece should overlap the lower course by at least 4 inches. Cut a hole in the roll roofing and slip it over as well. Embed both roofing pieces in cement. For added protection add a boot flashing.

Work from one side roof past the center of a valley by 2 feet. Then, working from the other side, overlap the valley, strike a chalkline, and trim the piece at the center of the valley. Keep nails at least 12 inches from the center of the valley; use a 4-inch-wide bed of roofingcement to attach everything that is closer than 12 inches.

In most cases you can simply overlap the sheets at the ridge using roofingcement and nails for the final piece. However if the final piece does not come down at least 8 inches past the peak, cover the peak with a 16-inch-wide strip that is embedded in cement.